Electronically controlled crossbar switch

ABSTRACT

A crossbar switch for a telecommunication system has relays with operating windings and holding windings positioned at the junctions of &#39;&#39;&#39;&#39;horizontal&#39;&#39;&#39;&#39; and &#39;&#39;&#39;&#39;vertical&#39;&#39;&#39;&#39; conductors individual to respective rows and columns, the operating windings of all relays of one row being connected at one end to a common row-control circuit and at their other ends to individual columncontrol circuits by way of these conductors. The two control circuits include controlled rectifiers which during certain periods receive operating voltage from a central power supply for the selective energization of a relay in response to concurrent firing pulses applied to the respective controlled rectifiers. A maintenance circuit, also including a normally deenergized controlled rectifier, energizes the holding winding of the selected relay in response to the firing of the controlled rectifier of the corresponding column-control circuit and subsequently releases that relay upon deactivation of its own controlled rectifier by a disconnect pulse.

United States Patent 1 3,621,147

[72] Inventor Giovanni Perucca Primary ExaminerKathleen H. Claffy Turin, Assistant Examiner-William A. Helvestine l PP 843,977 Attorney-Karl F. Ross [22] Filed Aug. 11, I969 [45] Patented Nov. 16, 1971 l [73] Assignee CSELT Centro Studi e Lboratori R Telecomunicazioni S.p.A. Turin, Italy [32] Priority Aug. 13, 1968 ABSTRACT: A crossbar switch for a telecommunication [33] Italy system has relays with operating windings and holding [3 l 52824-A/68 windings positioned at the junctions of horizontal" and vertical conductors individual to respective rows and columns, the operating windings of all relays of one row being conl ELECTRONICALLY CONTROLLED CROSSBAR nected at one end to a common row-control circuit and at SWITCH their other ends to individual column-control circuits by way 12 clllmsiznl'awing 8 of these conductors. The two control circuits include con- [52] Us. Cl U 179/18 GE trolled rectifiers which during certain periods receive operat- [5| 1 noq 3/42 ing voltage from a central power supply for the selective ener- 501 Field ofSearch [79/18 GE 8 relay in resPonse fifing Pulses plied to the respective controlled rectifiers. A maintenance 56] References Cited circuit, also including a normally deenergized controlled recti- UNITED STATES PATENTS fier, energizes the holding winding of the selected relay in response to the firing of the controlled rectifier of the cor- 3308244 3/1967 Bruglemans 179/18 GE responding column-control circuit and subsequently releases FOREIGN PATENTS that relay upon deactivation of its own controlled rectifier by a l,l46,53l 4/l963 Germany l79/l8 GE disconnect pulse.

COMMAND UNIT 1 ELECTRONICALLY CONTROLLED CROSSBAR SWITCH My present invention relates to a crossbar switch for telephone and other telecommunication systems wherein inselected junction.

Another object is to provide means in such a system for minimizing the consumption of electrical energy by the crossbar switch and associated circuitry, with virtually no power loss occurring at any nay unselected junction and in the control circuits assigned thereto.

It is also an object of this invention to provide a system of new connection.

In accordance with an important feature of my present invention, row-control circuits, column-control circuits and maintenance circuits for the several junction relays are provided with first, second and third controlled rectifiers, respec tively, the concurrent firing of a combination of first and second controlled rectifiers in a chosen row-control and column-control circuit during an operating period of a normally inoperative common power supply resulting in the energization of an operating winding of a selected fired third controlled rectifier.

According to a more specific feature of my invention, the firing of the third controlled rectifier is accomplished via a connection extending from the associated column-control circuit so as to occur upon the energization of the second controlled rectifier in the latter circuit. In the energized state of any junction relay, a lockout gate in the corresponding column-control circuit blocks the transmission of a firing pulse to the second controlled rectifier thereof in order to prevent the concurrent operation of relay in a column. The blocking signal, coinciding with the energization of the holding winding, occurs slightly after the appearance of the original firing pulse.

The above and other features of my invention will be described in greater detail hereinafter with reference to the accompanying drawing in which:

FIG. 1 is a block diagram showing a crossbar switch embodying my present improvement; and

FIG. 2 is a circuit diagram showing details of representation units included in the network ofFlG. 1.

In FIG. 1 l have shown the basic structure of my improved crossbar switch comprising a matrix MR of horizontal conductors l0,-l0,,, and vertical conductors ll,-ll,,, only the first and last as well as an intermediate conductor 10,,, 11,,- of each array being shown. it will be understood that, as in conventional crossbar switches these conductors are accompanied by respective line wires extending along intersecting rows and columns so as to form a multiplicity of junctions column, such as RE for the relay at the junction of conductors l0, and 11,, relay RE at the junction of conductors 10,, and 11 and Rli at the junction of conductors l0,,, and 11,,. As particularly indicated for relay RE which is representative of all other in aiding relationship therewith, relay having a holding armature re and a working armature The working armature, not further referred to hereinafter, serves to establish a connection between the associated horizontal and vertical line wires not shown.

REM-REM; of that row, to cond uctor 10,, and, in parallel with corresponding windings of all other relays RE,,,.-RE,,,,. of the same column, to conductor 11,,- by way of an individual diode D This winding, therefore, can be energized by the concurrent application of different voltages to the row conductor 10, and the column conductor 11,-. Holding winding HW of relay RE is connected between the front contact of armature re and a locking conductor 12,,- extending along column conductor 11,-, similar locking conductors l2, and 12,, have been ilfirst and the last column of the matrix MR served by conductors 11, and 11,,.

All the row conductors 10,... 10 10,, originate at respective row-control circuits IC,... IR IR,,,, similar column-control circuits IC,... IC IC,,are provided for the column conductors 11,... 11,-... 11,. These column-control circuits are paired with respective maintenance circuits IT,... IT IT, from which the locking conductors 12,... 12,... 12,, extend.

A command unit CU serves for the selective energization of any row and column conductor to operate one of a switching relays at a corresponding junction. For this purpose, unit CU has a first set of output lead a,... a a,,, for activating the circuits IR,... lR IR,,,, a second set of output leads b,... b b, for activating the circuits IC,... lC IC,,, a further lead c terminating at a common power supply PS, and an additional set of activating leads d,... d,,... d, for the circuits IT,... lT,,.... lT,,. Bus bars e and f extend from power supply PS to all the rowcontrol circuits IR, etc. and all the column-control circuits lC, etc. respectively.

I shall now describe, in connection with FIG. 2 and with particular reference to relay RE and the associated control and maintenance circuits IR,,, IC,,- and IT,,., the operation of the crossbar switch of FIG. 1 in the establishment and the release of a connection between two intersecting telephone lines.

Row-control unit lR, comprises a first solid-state e.g. silicon) controlled rectifier SCR, whose cathode is connected to a source of negative voltage E, its gate electrode being connected to the same source by way of a resistor R and to positive voltage +E via a condenser C, in series with a resistor R,. Command lead a from unit CU is tied to the junction of resistor R, and condenser C,. The anode of controlled rectifier SCR, is connected to bus bar 6 through a resistor R and is directly connected to the row conductor 10,, leading to the within unit IT k has its gate electrode connected to the junction of resistors R and R the latter resistor being shunted by a capacitor C The cathode of controlled rectifier SCR- is connected directly to potential E whereas the anode thereof is tied to conductor 12 leading to holding winding HW of relay RE Thus, winding HW is energizable upon the firing of the normally nonconductive controlled rectifier SCR in a circuit including the grounded armature re after the latter has been attracted by energization of winding OW.

Conductor 11, is also connected directly to the cathode of controlled rectifier SCR whose anode is linked by a wiref to the power supply PS; wire j and a companion wire f are jointly represented in FIG. I by the bus barf The gate electrode of controlled rectifier SCR, is also connected to the collector of a PNP-transistor Q whose emitter is tied to wire f through a resistor R Lead b emanating from command unit CU, is connected through an inverting gate IG to the base of transistor 0,, this gate being conductive in the presence of a relatively positive potential (ground) applied to an input q thereof via a diode I) and a resistor R Input q is also connected through a resistor R to the collector of an NPN- transistor whose emitter directly receives the negative voltage -E and is returned to its base through a resistor R the base being further coupled to lead d by way of a condenser C Normally reverse-biased diodes D (grounded), D (connected to negative voltage E) and D (grounded) serve to protect the controlled rectifiers SCR,, SCR SCR respectively, against transient overvoltages due to the inductivity of windings OW and I-IW upon deenergization of these windings.

Power supply PS comprises a two-stage transistor circuit including a first stage in the form of a PNP-transistor Q and a second stage constituted by an NPN-transistor Q and a PNP- transistor Q The base of transistor 0 is tied to lead c which, within unit CU, is shown normally connected to positive voltage +E through a switch SW which can be reversed to ground the base for a predetermined interval. Tl-Ie emitter of transistor 0 is connected to potential -+-E through a voltage divider consisting of two resistors R R whose junction is tied to the base of transistor 0 the collector of transistor 0 is connected directly to the base of transistor Q, and through a resistor R to negative potential E. The emitter of transistor O is connected directly to wires e andf and through resistor R to negative-voltage source E, its collector being grounded. The collector of transistor 0,, is connected directly to wire 1" and to ground through a resistor R its emitter being connected to positive voltage +E.

In the quiescent state of the system shown in FIG. 2, switch SW is in its illustrated position and all the circuits are deenergized; with negative potential E on all three electrodes of controlled rectifier SCR no current flows through that rectifier or through any of the associated resistors in unit IR,,. Transistor O is biased to cutoff, transistors Q and 0 being also nonconducting; controlled rectifier SCR is also con nected between equipotential points E whereas controlled rectifier SCR and transistor 0 are open-circuited except for the negligible current flow by way of diodes D and D Thus, the current consumption at this state is virtually nil.

When a junction of matrix MR is to be closed, switch SW in unit CU is briefly reversed to generate a negative pulse P on lead c whereby transistor 0;, is rendered conductive; pulse I may be periodically generated by a timer in command unit CU or may come into existence, in response to a selection signal, concurrently with a relatively short negative firing pulse P on lead 0,, and a simultaneous positive firing pulse P,, on lead b In any event, these firing pulses will occur only during an operating interval of power supply PS established by the enabling pulse P With the first transistor stage 0 conducting, the transistors Q and Q of the second stage are also carried to saturation whereby wire j is grounded and positive voltage +E appears on wiref', The trailing edge offiring pulse P breaks down the controlled rectifier SCR which thereupon remains conductive for the duration of enabling pulse P At the same time. the inverted firing pulse F from gate FIG. causes the switching transistor 0, to saturate and to fire the associated controlled rectifier SCR, whose conductivity also lasts for the remainder of the enabling interval. Relay winding OW, lying between the anode of the first controlled rectifier SCR, and the cathode of the second controlled rectifier SCR- is thus energized to attract its armature whereby ground potential is applied to the anode of the third controlled rectifier SCR via armature re and winding HW. After a short delay determined by the time constant of RC network C R controlled rectifer SCR also breaks down to maintain the relay RE operated notwithstanding the subsequent deenergization of winding OW upon termination of enabling pulse P Negative bias on gate input q, due to the breakdown of controlled rectifier SCR blocks the gate FIG. against transmission of further firing pulses P,, to transistor 0,, serving as a starting amplifier for controlled rectifier SCR for as long as the relay is thus operated.

When the connection so established is to be released, a disconnect pulse IP,, of positive polarity appears on lead a and, via coupling condenser C briefly renders transistor 0 conductive. Controlled rectifier SCR starved of current, is thereby cut off so that winding HW is deenergized and armature re reopens the holding circuit of relay RE The system is then returned to its nondissipative initial state.

It will be observed that, even with relay Re operated, only a local circuit from source E is closed while no power is consumed in units IR,, and IC, v after the selection phase has terminated.

In the system described above, negative-voltage source E is designed to supply operating current to the various controlled rectifiers and relay windings whereas positive-voltage source +5, is merely required to furnish biasing potentials to transistors 0 Q and to capacitor C,; the latter voltage, therefore, may be derived from a source of relatively low power. Naturally, not all the potentials +E and E need to have the same magnitude or to be obtained from the same source, so long as the desired cutoff conditions are maintained in the quiescent state.

Although switch SW has been illustrated diagrammatically as a mechanical contact, it will be understood that pulse P, as well as pulses P,,, P,, and P,, may be obtained electronically from logical circuitry with positive potential (+E denoting the state l and ground denoting the state 0."

I claim:

I. A cross bar switch forming a matrix of intersecting rows and columns with individual row conductors and column conductors, respectively; a multiplicity of relays at the junctions of respective columns and rows, each of said relays having an operating winding connected between the corresponding row and column conductors and a holding winding in series with an armature of the relay; a multiplicity of row-control circuits each including a normally nonconductive first controlled rectifier connected between a respective row conductor and a source of first operating potential for the operating windings of the associated relays; a multiplicity of column-control circuits each including a normally nonconductive second controlled rectifier connected between a respective column conductor and a source of second operating potential for the operating windings of the associated relays; a multiplicity of maintenance circuits each including a normally nonconductive third controlled rectifier connected between an ancillary conductor common to the holding windings of all the relays of a respective column and a source of operating potential for the energization of the holding winding of a selected relay by way of said armature; a normally inoperative common power supply for all said controlled rectifiers; switch means for temporarily activating said power supply; and selector means for transmitting a firing pulse to a combination of first and second controlled rectifiers in a chosen row-control and column circuit during an operating period of said power supply to energize the operating winding of a selected relay and for substanductive to cut off a previously fired third controlled rectifier, thereby releasing the corresponding relay.

2. A crossbar switch as defined in claim 1, wherein corresponding column-control circuits and maintenance circuits are provided with interconnecting leads for fin'ng said third controlled rectifiers in response to the energization of a corresponding second controlled rectiifer.

3. A crossbar switch as defined in claim 1 wherein all said controlled rectifiers are provided with reverse-biased shunt diodes for protecting same against transients.

4. A crossbar switch as defined in claim 1 wherein said first transistor stage and a second by said first stage, said second stage having output leads extending to said row-control and column-control circuits.

5. A crossbar switch as defined in claim 4 wherein said column-control circuits include respective starting amplifiers for said second controlled rectifiers, said second stage comprising a pair of output transistors for delivering a first operating voltage to said first and second controlled rectifiers and a second operating voltage to said starting transistors.

6. A crossbar switch as defined in claim 1 wherein said selector means forms part of a command unit common to all said row-control and column-control circuits, said power supply being controlled from said command unit.

7. A crossbar switch forming a matrix of intersecting rows and columns with individual row conductors and column conductors, respectively; a multiplicity of relays at the junctions of respective columns and rows, each of said relays having an operating winding connected between the corresponding row and column conductors and a holding winding in series with an armature of the relay; a multiplicity of row-control circuits each including a normally nonconductive first controlled rectifier connected between a respective row conductor and a a source of second operating potential for the associated relays; a multiplicity of maintenance circuits each including a normally nonconductive third controlled rectifier connected between an ancillary conductor common to the holding windings of all the relays of column and a source of operating potential for the energization of the holding winding of a selected relay by way of said armature; a normally inoperative common power supply for all said controlled rectifiers; switch means for temporarily activating said power supply; and selector means for transmitting a firing pulse to a combination of first and second controlled rectifiers in a chosen row-control and column-'control circuit during an operating period of said power supply to energize the operating winding of a selected relay and for subsequently firing a third controlled rectifier in a corresponding maintenance circuit to energize the holding winding of said selected relay, said column-control circuits being provided with gate means responsive to energization of the third controlled rectifier in a corresponding maintenance circuit for blocking the application of a firing pulse to said second controlled rectifiers; said maintenance circuits being provided with inputs for receiving disconnect pulses deenergizing a previously fired third controlled rectifier to release the corresponding relay.

8. A crossbar switch as defined in claim 7 wherein corresponding column-control circuits and maintenance circuits are provided with interconnecting leads for firing said third controlled rectifiers in response to the energization of a correspondin second controlled rectifier, said leads bein rovlded WI delay networks for retardlng the energization of said third controlled rectifiers.

9. A crossbar switch as defined in claim 7 wherein said maintenance circuits are provided with normally nonconductive transistors shunting said third controlled rectifiers, said inputs terminating at said transistors for rendering same conductive to cut off the associated controlled rectifiers.

10. A crossbar switch forming a matrix of intersecting rows and columns with individual row conductors and column conductors, respectively; a multiplicity of relays at the junctions of respective columns and rows, each of said relays having an an armature of the relay; a multiplicity of row-control circuits each including a normally nonconductive first controlled rectifier connected between a respective row conductor and a source of first operating potential for the operating windings of the associated relays; a multiplicity of column-control circuits each including a normally nonconductive second controlled rectifier connected between a respective column conductor, a starting amplifier for said second controlled rectifier and a source of second operating potential for the operating third controlled rectifier connected between an ancillary conductor common to the holding windings of all the relays of a respective column and a source of operating potential for the energization of the holding winding of a selected relay by way of said armature; a normally inoperative common power supply for all said controlled rectifiers; switch means for temporarily activating said power supply; and selector means for transmitting a firing pulse to a combination of first and second corresponding maintenance circuit to energize the holding winding of said selected relay, said maintenance circuits being provided with inputs for receiving disconnect pulses deenergizing a previously fired third controlled rectifier to release the corresponding relay; said power supply comprising a first transistor stage and a second transistor stage controlled by said first stage, said second stage including a pair of output transistors for delivering a first operating voltage to said first and second controlled rectifiers and a second operating voltage to said starting transistors.

11. A crossbar switch as defined in claim 10 wherein said column-control circuits are provided with gate means responsive to energization of the third controlled rectifier in a corresponding maintenance circuit for blocking the application of a firing pulse to said second controlled rectifiers.

12. A crossbar switch as defined in claim 10 where in said output transistors are of opposite conductivity types and said operating voltages are of opposite polarities. 

1. A cross bar switch forming a matrix of intersecting rows and columns with individual row conductors and column conductors, respectively; a multiplicity of relays at the junctions of respective columns and rows, each of said relays having an operating winding connected between the corresponding row and column conductors and a holding winding in series with an armature of the relay; a multiplicity of row-control circuits each including a normally nonconductive first controlled rectifier connected between a respective row conductor and a source of first operating potential for the operating windings of the associated relays; a multiplicity of column-control circuits each including a normally nonconductive second controlled rectifier connected between a respective column conductor and a source of second operating potential for the operating windings of the associated relays; a multiplicity of maintenance circuits each including a normally nonconductive third controlled rectifier connected betwEen an ancillary conductor common to the holding windings of all the relays of a respective column and a source of operating potential for the energization of the holding winding of a selected relay by way of said armature; a normally inoperative common power supply for all said controlled rectifiers; switch means for temporarily activating said power supply; and selector means for transmitting a firing pulse to a combination of first and second controlled rectifiers in a chosen row-control and column circuit during an operating period of said power supply to energize the operating winding of a selected relay and for substantially simultaneously firing a third controlled rectifier in a corresponding maintenance circuit to energize the holding winding of said selected relay; said maintenance circuits being provided with normally nonconductive transistors shunting said third controlled rectifiers, said transistors having inputs connected to receive disconnect pulses for rendering same conductive to cut off a previously fired third controlled rectifier, thereby releasing the corresponding relay.
 2. A crossbar switch as defined in claim 1, wherein corresponding column-control circuits and maintenance circuits are provided with interconnecting leads for firing said third controlled rectifiers in response to the energization of a corresponding second controlled rectiifer.
 3. A crossbar switch as defined in claim 1 wherein all said controlled rectifiers are provided with reverse-biased shunt diodes for protecting same against transients.
 4. A crossbar switch as defined in claim 1 wherein said power supply comprises a first transistor stage and a second transistor stage controlled by said first stage, said second stage having output leads extending to said row-control and column-control circuits.
 5. A crossbar switch as defined in claim 4 wherein said column-control circuits include respective starting amplifiers for said second controlled rectifiers, said second stage comprising a pair of output transistors for delivering a first operating voltage to said first and second controlled rectifiers and a second operating voltage to said starting transistors.
 6. A crossbar switch as defined in claim 1 wherein said selector means forms part of a command unit common to all said row-control and column-control circuits, said power supply being controlled from said command unit.
 7. A crossbar switch forming a matrix of intersecting rows and columns with individual row conductors and column conductors, respectively; a multiplicity of relays at the junctions of respective columns and rows, each of said relays having an operating winding connected between the corresponding row and column conductors and a holding winding in series with an armature of the relay; a multiplicity of row-control circuits each including a normally nonconductive first controlled rectifier connected between a respective row conductor and a source of first operating potential for the operating windings of the associated relays; a multiplicity of column-control circuits each including a normally nonconductive second controlled rectifier connected between a respective column conductor and a source of second operating potential for the operating windings of the associated relays; a multiplicity of maintenance circuits each including a normally nonconductive third controlled rectifier connected between an ancillary conductor common to the holding windings of all the relays of a respective column and a source of operating potential for the energization of the holding winding of a selected relay by way of said armature; a normally inoperative common power supply for all said controlled rectifiers; switch means for temporarily activating said power supply; and selector means for transmitting a firing pulse to a combination of first and second controlled rectifiers in a chosen row-control and column-control circuit during an operating period of said power supply to energize the operating winding of a selected reLay and for subsequently firing a third controlled rectifier in a corresponding maintenance circuit to energize the holding winding of said selected relay, said column-control circuits being provided with gate means responsive to energization of the third controlled rectifier in a corresponding maintenance circuit for blocking the application of a firing pulse to said second controlled rectifiers; said maintenance circuits being provided with inputs for receiving disconnect pulses deenergizing a previously fired third controlled rectifier to release the corresponding relay.
 8. A crossbar switch as defined in claim 7 wherein corresponding column-control circuits and maintenance circuits are provided with interconnecting leads for firing said third controlled rectifiers in response to the energization of a corresponding second controlled rectifier, said leads being provided with delay networks for retarding the energization of said third controlled rectifiers.
 9. A crossbar switch as defined in claim 7 wherein said maintenance circuits are provided with normally nonconductive transistors shunting said third controlled rectifiers, said inputs terminating at said transistors for rendering same conductive to cut off the associated controlled rectifiers.
 10. A crossbar switch forming a matrix of intersecting rows and columns with individual row conductors and column conductors, respectively; a multiplicity of relays at the junctions of respective columns and rows, each of said relays having an operating winding connected between the corresponding row and column conductors and a holding winding in series with an armature of the relay; a multiplicity of row-control circuits each including a normally nonconductive first controlled rectifier connected between a respective row conductor and a source of first operating potential for the operating windings of the associated relays; a multiplicity of column-control circuits each including a normally nonconductive second controlled rectifier connected between a respective column conductor, a starting amplifier for said second controlled rectifier and a source of second operating potential for the operating windings of the associated relays; a multiplicity of maintenance circuits each including a normally nonconductive third controlled rectifier connected between an ancillary conductor common to the holding windings of all the relays of a respective column and a source of operating potential for the energization of the holding winding of a selected relay by way of said armature; a normally inoperative common power supply for all said controlled rectifiers; switch means for temporarily activating said power supply; and selector means for transmitting a firing pulse to a combination of first and second controlled rectifiers in a chosen row-control and column-control circuit during an operating period of said power supply to energize the operating winding of a selected relay and for substantially simultaneously firing a third controlled rectifier in a corresponding maintenance circuit to energize the holding winding of said selected relay, said maintenance circuits being provided with inputs for receiving disconnect pulses deenergizing a previously fired third controlled rectifier to release the corresponding relay; said power supply comprising a first transistor stage and a second transistor stage controlled by said first stage, said second stage including a pair of output transistors for delivering a first operating voltage to said first and second controlled rectifiers and a second operating voltage to said starting transistors.
 11. A crossbar switch as defined in claim 10 wherein said column-control circuits are provided with gate means responsive to energization of the third controlled rectifier in a corresponding maintenance circuit for blocking the application of a firing pulse to said second controlled rectifiers.
 12. A crossbar switch as defined in claim 10 where in said output transistors are of opposite conductivity types anD said operating voltages are of opposite polarities. 